Pilot valve

ABSTRACT

A pilot valve that includes a pilot valve body including a chamber, a first fluid inlet and a second fluid inlet for providing fluid to the chamber, and a fluid outlet for receiving fluid from the chamber. The pilot valve further includes a separating element and a valve rod, the valve rod is arranged to control fluid flow from the first or second fluid inlet to the fluid outlet via the chamber. The separating element is connected to, and movable with the valve rod, and has a first fluid contacting area configured to be in fluid communication with the first fluid inlet, and a second fluid contacting area configured to be in fluid communication with the second fluid inlet and arranged on an opposite side to the first fluid contacting area. The pilot valve is at least partly controlled by a difference between a first force and a second forces acting on the first and second fluid contacting areas of the separating element.

TECHNICAL FIELD OF THE INVENTION

The present inventive concept relates to a pilot valve for delivering a fluid flow to, or being in fluid communication with, a piloted or main valve. The present inventive concept further relates to a fluid distribution system comprising a pilot valve.

BACKGROUND OF THE INVENTION

A pilot valve is used to control a limited-flow control feed to a piloted valve, also referred to as a main valve. The piloted valve may e.g. be arranged in risers and branches of heating and cooling systems used in various domestic and industrial applications.

The pilot valve is typically a smaller valve compared to the piloted valve, and is advantageous to use because a small and easily operated feed from the pilot valve may be used to control a much higher pressure or higher flow feed of the piloted valve, which would otherwise require a much larger force to operate. Pilot valves are conventionally positioned externally of the body of the piloted valve and are connected to the body by one or more fluid conduits which have an outlet into the main flow area of the piloted valve chamber.

Pilot valves have external and internal fluid paths enabling fluid flow at different pressures to be fed to/from the piloted valve, or allowing for the piloted valve to be in fluid communication with different fluid paths at different pressures. Theses fluid paths are often complex and require e.g. many internal and external fluid conduits to be connected to and from the pilot valve.

The present inventive concept seeks to provide a pilot valve which is less complex and easier to use for regulating the piloted valve.

SUMMARY OF THE INVENTION

An object of the inventive concept is to overcome the above problems, and to provide for a pilot valve which, at least to some extent, is less complex than prior art solutions. This, and other objects, which will become apparent in the following, are accomplished by means of a pilot valve and a fluid distribution system comprising a pilot valve defined in the accompanying claims.

The present inventive concept is based on the insight that the internal fluid paths of the pilot valve can be made less complex, and be more flexible in use, if fluid from two inlets are fed to opposite surfaces of a separating element for at least partly control the movement of a valve rod, and where the position of the valve rod determines which of the inlets are allowed to be in fluid communication with a fluid outlet of the pilot valve.

According to at least a first aspect of the present inventive concept, a pilot valve is provided. The pilot valve comprises:

a pilot valve body comprising: a chamber, a first fluid inlet and a second fluid inlet for providing fluid to said chamber, and a fluid outlet for receiving fluid from said chamber;

a valve rod arranged at least partly inside said chamber, said valve rod being configured to control fluid flow from said first fluid inlet to said fluid outlet via said chamber, and configured to control fluid flow from said second fluid inlet to said fluid outlet via said chamber;

a separating element being connected to, and movable with said valve rod, said separating element having a first fluid contacting area, and a second fluid contacting area arranged on an opposite side to said first fluid contacting area,

said first fluid contacting area being configured to be in fluid communication with said first fluid inlet for applying a first force to said separating element, and

said second fluid contacting area being configured to be in fluid communication with said second fluid inlet for applying a second force to said separating element;

wherein a difference between said first and second forces controls the movement of the separating element and the valve rod in such a way that said valve rod in at least a first position provides for a fluid communication between said first fluid inlet and said fluid outlet; and in at least a second position provides for a fluid communication between said second fluid inlet and said fluid outlet.

Hereby, internal fluid flow paths inside the pilot valve, that is fluid from the first fluid inlet and fluid from the second fluid inlet, may be used to control the separating element and the valve rod. The valve rod then controls which of the first and second fluid inlets that are allowed to be in fluid communication with the fluid outlet. That is, fluid from the first and second fluid inlets, which are used to control the piloted valve, are also used to control the position of the valve rod. Hence, the external fluid conduits providing fluid flow to the pilot valve may be reduced. Furthermore, regardless of the position of the valve rod, i.e. whether fluid from the first fluid inlet or fluid from the second fluid inlet is allowed to be in fluid communication with the fluid outlet, the first fluid contacting area is arranged to be in fluid communication with said first fluid inlet, and the second fluid contacting area is arranged to be in fluid communication with said second fluid inlet.

It should be understood that when the pilot valve is correctly installed to a piloted valve and to the fluid distribution system where the piloted valve is installed, a static pressure of fluid from the first fluid inlet acts on the first fluid contacting area of the separating element to exert the first force on the separating element, and a static pressure of fluid from the second fluid inlet acts on the second fluid contacting area of the separating element to exert the second force on the separating element. The first force and the second force acts at least partly in opposite directions, i.e. at least one of the component of the first force act in an opposite direction of at least one of the component of the second force.

It should be noted that fluid communication implies that there is a pressurized connection. For example, if the first fluid inlet is in fluid communication with the fluid outlet, the first fluid inlet will be in pressurized connection with the fluid outlet. Hence, the static pressure of fluid at the first fluid inlet will be, essentially, the same as the static pressure of fluid at the fluid outlet.

According to at least one example embodiment, a first internal fluid conduit within said pilot valve body fluidly connects said first fluid inlet with the chamber, a second internal fluid conduit within said pilot valve body fluidly connects said second fluid inlet with the chamber, and a third internal fluid conduit within said pilot valve body fluidly connected said chamber with the fluid outlet.

It should be noted that fluid inside the pilot valve is more or less static, i.e. there is generally no fluid flow inside the pilot valve, but rather redistribution of fluid, and different pressurized connections, due to movement of the separating element and the valve rod. Hence, when stating that there is a fluid flow between two locations, it should be interpreted as that fluid is allowed to flow between the two locations, and that the two locations are in pressurized connection by a fluid communication between the two locations.

According to at least one example embodiment, said chamber comprises a first chamber portion arranged to receive fluid from said first fluid inlet, and a second chamber portion arranged to receive fluid from said second fluid inlet, wherein when said valve rod is in said first position, said first fluid inlet, said first chamber portion and said fluid outlet are in fluid communication with each other, and said second fluid inlet is restricted from being in fluid communication with said fluid outlet by said valve rod; and wherein when said valve rod is in said second position said second fluid inlet, said second chamber portion and said fluid outlet are in fluid communication with each other, and said first fluid inlet is restricted from being in fluid communication with said fluid outlet by said valve rod.

Hereby, only fluid from one of the first or second fluid inlets is allowed to be in fluid communication with the fluid outlet. Thus, the pilot valve may feed a fluid to the piloted valve, or rather allow for the piloted valve to be in fluid communication with the fluid outlet of the pilot valve, of a predetermined pressure corresponding to the static pressure of either the first fluid inlet or the second fluid inlet.

It should be noted that when the valve rod is in its first position, the fluid outlet is prevented from being in fluid communication with the second chamber portion, and when the valve rod is in its second position, the fluid outlet is prevented from being in fluid communication with the first chamber portion.

According to at least one example embodiment, said valve rod in at least an intermediate position provides for no fluid communication between said first fluid inlet and said fluid outlet, and no fluid communication between said second fluid inlet and said fluid outlet. Hence both fluid from the first and the second fluid inlets are restricted from being in fluid communication with the fluid outlet.

According to at least one example embodiment, said chamber comprises a third chamber portion arranged between said first and second chamber portions, and wherein said fluid outlet is arranged to receive fluid from said chamber via said third chamber portion.

Hence, when the valve rod is in its first position, the first and third chamber portions are in fluid communication. When the valve rod is in its second position the second and third chamber portions are in fluid communication. When the valve rod is in its intermediate position, neither the first nor the second chamber portions are in fluid communication with the third chamber portion.

According to at least one example embodiment, said valve rod comprises a fluid conduit for guiding a fluid flow from said first chamber portion to said first fluid contacting area of the separating element in such a way that said first fluid inlet is in fluid communication with said first fluid contacting area.

Hereby, an internal fluid path within the pilot valve is provided for. According to at least one example embodiment, the valve rod is hollow and provided for an internal fluid conduit within the valve rod. Thus, the pilot valve may be referred to as a tree-way pilot valve providing for a first fluid path between the first fluid inlet and the fluid outlet, a second fluid path between the second fluid inlet and the fluid outlet, and a third fluid path between the first fluid inlet and the first fluid contacting area, via the fluid conduit of the valve rod.

According to at least one example embodiment, said fluid conduit of the valve rod extends through said separating element.

Hereby, fluid from the first fluid inlet may be in fluid communication with the first fluid contacting area of the separating element, via the valve rod. This provides for a beneficial internal fluid path within the pilot valve.

According to at least one example embodiment, the valve rod may extend through the separating element. According to at least one example embodiment, the valve rod is connected to the separating element, and the fluid conduit of the valve rod extends beyond said valve rod and through said separating element.

According to at least one example embodiment, said separating element fluidly separates said first fluid contacting area of said separating element from said second fluid contacting area.

Hereby, the first fluid contacting area and the second fluid contacting area may be exposed to fluids with different pressures.

According to at least one example embodiment, the pilot valve comprises a valve housing, wherein said valve body, said valve rod and said separating element are comprised in said valve housing, and said valve housing further comprises a pilot spring arranged to exert a force on at least a part of said first fluid contacting area.

The pilot spring may for example be housed inside a pilot spring housing defining a pilot spring chamber. Thus the separating element may fluidly separate the chamber from the pilot spring chamber.

According to at least one example embodiment, said pilot spring is an adjustable pilot spring.

According to at least one example embodiment, said first fluid contacting area of said separating element is facing said pilot spring, and said second fluid contacting area of said separating element is facing said chamber.

Hence, when the separating element, and the valve rod, moves from its first position to e.g. its second position, the separating element will be moved towards the pilot spring and pilot spring chamber.

According to at least one example embodiment, said valve rod is configured to be moved from its first position to its second position if a combined force applied to said first fluid contacting area by said pilot spring and fluid in fluid communication with said first fluid inlet is smaller than said second force applied to said second fluid contacting area by fluid in fluid communication with said second fluid inlet.

By using a spring, the movement of the separating element, and the movement of the valve rod and hence the control of which fluid inlet to be in fluid communication with the fluid outlet, are easier controlled.

According to at least one example embodiment, the pilot valve further comprises at least a first sealing element and a second sealing element, and wherein said first chamber portion is arranged to be fluidly sealed from said third chamber portion by a sealing contact between said valve rod and said first sealing element when said valve rod is in said second position, and wherein said second chamber portion is arranged to be fluidly sealed from said third chamber portion by a sealing contact between said valve rod and said second sealing element when said valve rod is in said first position.

The third chamber portion may comprise both the first and the second sealing elements. According to at least one example embodiment, a first geometrical chamber cross section in said chamber tangents the first sealing element and a second geometrical chamber cross section in said chamber tangents the second sealing element. The third chamber portion may at least partly be defined by a portion of the chamber extending between the first geometrical chamber cross section and the second geometrical chamber cross section. According to at least one example embodiment, the third chamber portion is at least partly defined by the fluid outlet or the inlet to the third internal fluid conduit fluidly connecting said chamber with said fluid outlet.

According to at least one example embodiment, the first chamber portion may at least party be defined by the first fluid inlet or the inlet to the chamber from the first internal fluid conduit, and the first geometrical chamber cross section or the third chamber portion.

According to at least one example embodiment, the second chamber portion may at least party be defined by the second fluid inlet or the inlet to the chamber from the second internal fluid conduit, and the second geometrical chamber cross section or the third chamber portion.

According to at least one example embodiment, the third chamber portion is arranged directly between the first and the second chamber portions.

According to at least one example embodiment, said valve rod has at least a first valve rod portion, a second valve rod portion, and a third valve rod portion arranged between said first and second valve rod portions, each of said first and second valve rod portions having a diameter larger than a diameter of said third valve rod portion.

The third valve rod portion may for example be waist shaped, or hour-glass shaped, and the first and the second valve rod portions may have a constant diameter. According to at least one example embodiment, a diameter of the first valve rod portion is larger than a diameter of the second valve rod portion. According to at least one example embodiment, a diameter of the first valve rod portion is smaller than a diameter of the second valve rod portion. According to at least one example embodiment, a diameter of the first valve rod portion is of the same size as a diameter of the second valve rod portion.

The first, second and third valve rod portions may have a circular cross section, the first and the second valve rod portions may e.g. be cylindrically shaped. Furthermore, the chamber, and the first, second and third chamber portions may have a circular cross section.

According to at least one example embodiment, when said valve rod is in its first position, said third valve rod portion is arranged to be at least partly located in said first chamber portion such that said first fluid inlet is in fluid communication with said fluid outlet via said first and third chamber portions, and said second valve rod portion is arranged to be at least partly located in both said second chamber portion and said third chamber portion such that said second fluid inlet is restricted from being in fluid communication with said fluid outlet.

According to at least one example embodiment, when said valve rod is in its second position, said third valve rod portion is arranged to be at least partly located in said second chamber portion such that said second fluid inlet is in fluid communication with said fluid outlet via said second and third chamber portions, and said first valve rod portion is arranged to be at least partly located in both said first chamber portion and said third chamber portion such that said first fluid inlet is restricted from being in fluid communication with said fluid outlet.

Hereby, fluid communications between the first and second inlets, and the fluid outlet are provided at least partly by the position of the valve rod inside the chamber. According to at least one example embodiment, fluid communication between the first and second inlets, and the fluid outlet are provided at least partly by the shape of the valve rod.

According to at least one example embodiment, said separating element comprises a piston. According to at least one example embodiment, said separating element comprises a membrane. According to at least one example embodiment, said second fluid contacting area is comprised in said membrane or said piston.

The second fluid contacting area of the membrane may be made larger than the second fluid contacting area of the piston. Furthermore, a membrane is less susceptible to friction losses, and leakage, compared to the piston. Hence, the control feed to the piloted valve may be more precisely controlled when using a membrane compared to a piston. However, a piston may be preferred as it is cheaper to produce compared to a membrane.

The piloted valve to be controlled may any type of valve suitable for being controlled by a pilot valve. The piloted valve may e.g. be a normally open valve, or it may be a normally closed valve.

According to at least a second aspect of the present inventive concept, a fluid distribution system is provided. The fluid distribution system comprises:

a pilot valve as described in relation to the first aspect of the present inventive concept, and a first fluid conduit for guiding a fluid to said first fluid inlet, a second fluid conduit for guiding a fluid to said second fluid inlet, and a third fluid conduit for guiding fluid away from said fluid outlet, wherein a static pressure of fluid in said first fluid conduit is lower compared to a static pressure of fluid in said second fluid conduit.

According to at least a third aspect of the present inventive concept, a valve arrangement is provided. The valve arrangement comprises a pilot valve as described in relation to the first aspect of the present inventive concept or a fluid distribution system as described in relation to the second aspect of the present inventive concept, and a piloted valve in fluid communication with the pilot valve of the first or second aspects of the present inventive concept.

The piloted valve may be any type of valve arranged to be connected to a pilot valve.

BRIEF DESCRIPTION OF THE DRAWINGS

The present inventive concept will now be described in more detail, with reference to the appended drawings showing example embodiments, wherein:

FIG. 1 illustrates in cross section a piloted valve and a pilot valve according to at least one example embodiment of the inventive concept;

FIG. 2a illustrates a pilot valve in cross section according to at least one example embodiment of the inventive concept;

FIG. 2b illustrates a pilot valve arrangement comprising a pilot valve, or a first pilot valve part according to at least one example embodiment of the inventive concept, and a second pilot valve part;

FIGS. 3-7 illustrates different states and valve rod positions of a pilot valve arrangement comprising a pilot valve, or a first pilot valve part according to at least one example embodiment of the inventive concept, and a second pilot valve part;

FIG. 8 is a schematic illustration of a fluid distribution system with a pilot valve arrangement comprising a pilot valve, or a first pilot valve part according to at least one example embodiment of the inventive concept, and a second pilot valve part;

FIG. 9 is a schematic illustration of a fluid distribution system and a pilot valve according to at least one example of the inventive concept;

FIG. 10 is a schematic illustration of a fluid distribution system and a pilot valve according to at least one example of the inventive concept.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following description, the present inventive concept is described with reference to a pilot valve, a pilot valve arrangement comprising said pilot valve, also referred to as a first pilot valve part in the following text, and a second pilot valve part. The present inventive concept is also described with reference to a fluid distribution system comprising such pilot valve and/or such pilot valve arrangement and a piloted valve. As the pilot valve in the following text is referred to as a first pilot valve part when comprised in a pilot valve arrangement, features of the pilot valve as described above are sometimes renamed accordingly. For example the fluid outlet of the pilot valve is referred to as a first pilot valve fluid outlet when the pilot valve as described above is a first pilot valve part comprised in a pilot valve arrangement.

FIG. 1 illustrates in cross section a pilot valve 1 and a piloted valve 3, also referred to as a main valve 3. The pilot valve 1 is typically a smaller valve 1 compared to the piloted valve 3, and is used to control a limited-flow control feed to the piloted valve 3. The pilot valve 1 is advantageous to use because a small and easily operated feed from the pilot valve 1 may be used to control a much higher pressure or higher flow feed of the piloted valve 1, which would otherwise require a much larger force to operate.

The pilot valve 1 in FIG. 1 comprises a chamber 10, a first fluid inlet 20 arranged to be fluidly fed from an internal fluid flow path from the piloted valve 3, and a second fluid inlet 22 arranged to be fluidly fed from an external fluid flow (not shown), wherein both the first and the second fluid inlets 20, 22 are arranged to provide fluid to the chamber 10. The pilot valve 1 further comprises a fluid outlet 24 for receiving fluid from the chamber 10 and for providing a fluid control feed to the piloted valve 3. As illustrated in FIG. 1, a valve rod 30 arranged at least partly inside the chamber 10 is arranged to control fluid flow from the first and second fluid inlets 20, 22 to the fluid outlet 24.

The piloted valve 3, or the main valve 3, may be any type of valve arranged to be connected to a pilot valve. In FIG. 1, the piloted valve is a two-plug valve having two separated force contacting surfaces 2 a, 2 b which the fluid control feed from the pilot valve 1 may act on. The piloted valve 3 may be a normally open valve. According to one example, the piloted valve 3 may be a normally closed valve.

FIG. 2a illustrates a pilot valve 101 in cross section, similar to the pilot valve 1 shown in FIG. 1, but in greater detail. The pilot valve 101 in FIG. 2a comprises a first pilot valve body 102 having a chamber 110, a first fluid inlet 120 and a second fluid inlet 122 for providing fluid to the chamber 110 via a first internal fluid conduit 121 and a second internal fluid conduit 123. The first pilot valve body 102 further comprises a pilot valve fluid outlet 124 for receiving fluid from the chamber 110 via an internal pilot valve fluid outlet conduit 125, and providing a control feed to a piloted valve (as shown in FIG. 1). As illustrated in FIG. 2a , a valve rod 130 is arranged at least partly inside the chamber 110 for controlling fluid flow from the first and second fluid inlets 120, 122 to the fluid outlet 124 of the pilot valve, via the chamber 110.

The pilot valve 101 in FIG. 2a further comprises a separating element 140 being connected to, and movable with the valve rod 130. In FIG. 2a , the separating element 140 comprises a disc 141 having a first fluid contacting area 142, and a membrane 143 having a second fluid contacting area 144. The first fluid contacting area 142 of the separating element 140 is arranged at least partly opposite to the second fluid contacting area 144. According to at least one example embodiment, the separating element 140 may comprise a piston instead of the membrane 140. Furthermore, even though the separating element 140 in FIG. 2a comprises two parts 141, 143, the separating element 140 may comprise only one part.

The pilot valve 101 further comprises a pilot spring 160 housed in a pilot spring housing 162 defining a pilot spring chamber 163, the pilot spring 160 being arranged inside the pilot spring chamber 163, between a wall portion 164 in the pilot spring housing 162 and the first fluid contacting area 142. The wall portion 164 is facing the first fluid contacting area 142. Furthermore, a valve housing 150 comprises the valve body 102, the valve rod 130, the separating element 140, the pilot spring 160 and the pilot spring housing 162.

As illustrated in FIG. 2a , a valve rod fluid conduit 132 is arranged inside the valve rod 130 and extends from the chamber 110, via a valve rod fluid conduit inlet 132 a in the valve rod 130, through the valve rod 130 and through the separating element 140, whereby fluid from the first fluid inlet 120 is enabled to be in fluid communication with fluid in the pilot spring chamber 163. Hereby, the first fluid inlet 120 is enabled to be in fluid communication with the first fluid contacting area 142 within the pilot spring housing 162. Furthermore, the separating element 140 fluidly separates fluid from the second fluid inlet 122, which fluid exerts a pressure on the second fluid contacting area 144, from fluid from the first fluid inlet 120, which fluid exerts a pressure on the first fluid contacting area 142. Hence, fluid from the second fluid inlet 122 is fluidly separated from fluid in the pilot spring chamber 163 by the separating element 140.

The chamber 110 and the valve rod 130 have preferably circular cross sections. Hereby, sealing elements such as o-rings may be used to seal different chamber portions from each other. However, other shapes and other cross sections of the chamber 110 and the valve rod 130 are possible to use.

The function of the pilot valve 101 of FIG. 2a will now be described in more detail.

As fluid from the first fluid inlet 120 is enabled to be in fluid communication with the first fluid contacting area 142 of the separating element 140, the fluid may exert a pressure on the first fluid contacting area 142 in order for a first force to be applied to the separating element 140. Fluid from the second fluid inlet 122 is enabled to be in fluid communication with the second fluid contacting area 144 of the separating element 140 and may thereby exert a pressure on the second fluid contacting area 144 to apply a second force to the separating element 140. Since the first fluid contacting area 142 is arranged on an opposite side to the second fluid contacting area 144, the first and the second force act on the separating element 140 in opposite directions. The first force acts on the separating element 140 in a direction from the first fluid contacting area 142 at least partly towards the second fluid contacting area 144, and the second force acts on the separating element in a direction from the second fluid contacting area 144 at least partly towards the first fluid contacting area 142.

As illustrated in FIG. 2a , the pilot spring 160 arranged in the pilot spring housing 162 between the wall portion 164 and the first fluid contacting area 142, acts on the separating element 140 with a pilot spring force in at least partly the same direction as the first force. Hence, a combined force comprising the first force and the pilot spring force act on the separating element 140 in one direction, and the second force act on the separating element 140 in at least partly, an opposite direction. A difference between the combined force and the second force will normally cause a movement and/or a change in the movement of the separating element 140 and the valve rod 130, as the separating element 140 is arranged to move together with the valve rod 130.

In a first position of the valve rod 130, fluid from the first fluid inlet 120 is enabled to be in fluid communication with the pilot valve fluid outlet 124, and in a second position of the valve rod 130, fluid from the second fluid inlet 122 is enabled to be in fluid communication with the pilot valve fluid outlet 124. It should be understood that the valve rod 130 may be slightly moved within each of the first and second positions, as the first and the second positions are defined by which fluid inlet 120, 122 that is in fluid communication with the pilot valve fluid outlet 124. There is also an intermediate position of the valve rod 130, between its first and second positions where none of the fluid inlets 120, 122 are in fluid communication with the pilot valve fluid outlet 124. The different positions of the valve rod 130 will be described in greater detail with reference to FIGS. 3-7.

FIG. 2b illustrates a pilot valve arrangement 301 comprising a first pilot valve part 101, described as the pilot valve 101 in FIG. 2a , and a second pilot valve part 201 arranged between the first pilot valve part 101 and a piloted valve (the piloted valve 3 shown only in FIG. 1). The fluid outlet 124 from the first pilot valve part 101, hereafter referred to as the first pilot valve fluid outlet 124, is fed to the second pilot valve part 201 instead of directly to a piloted valve as shown in FIG. 1. A fluid outlet 224 of the second pilot valve part 201 is fed to the piloted valve.

The first pilot valve part 101 and the second pilot valve part 201 as described with reference to FIGS. 2a-2b will now be described in further detail with reference to FIGS. 3-7. First, the pilot valve 101, or the first pilot valve part 101, will be described, second, the second pilot valve part 201 will be described, and third, the structure and function of the pilot valve arrangement 301 comprising the first pilot valve part 101 and the second pilot valve part 201 will be described. The first valve part 101 in FIGS. 2a-2b is the same as the first valve part 101 in FIGS. 3-7, and the second valve part 201 in FIG. 2b is the same as the second valve part 201 in FIG. 3-7, hence, the same reference numerals will be used for referring to the same features. Thus, FIGS. 3-7 disclose different states and valve rod positions of the first and second valve parts 101, 102 of FIGS. 2a-2b . Therefore, in order to facilitate the reading comprehension, some reference numerals are only indicated in the Figure where first described.

As indicated in FIG. 3, the first pilot valve part 101 in FIGS. 3-7 comprises a first sealing element 112 in the form of an o-ring 112, and a second sealing element 114 in the form of an o-ring 114. The first sealing element 112 is arranged within the chamber 110 and a first geometrical chamber cross section 112 a tangents the first sealing element 112. The second sealing element 114 is arranged within the chamber 110 and a second geometrical chamber cross section 114 a tangents the second sealing element 114. The chamber 110 comprises a first chamber portion 110 a, a second chamber portion 110 b and a third chamber portion 110 c arranged between the first and second chamber portions 110 a, 110 b. The third chamber portion 110 c comprises both the first and the second sealing elements 112, 114 and is at least partly defined by the portion 110 c of the chamber 110 extending between first geometrical chamber cross section 112 a and the second geometrical chamber cross section 114 a. The first chamber portion 110 a is at least partly defined by the portion 110 a of the chamber 110 extending between the third chamber portion 110 c and the first fluid inlet 120, or an inlet of the first internal fluid inlet conduit 121 to the chamber 110. The second chamber portion 110 b is at least partly defined by the portion 110 b of the chamber 110 extending between the third chamber portion 110 c and the second fluid inlet 122 or an inlet of the second internal fluid inlet conduit 123 to the chamber 110. The first chamber portion 110 a is arranged to receive fluid from the first fluid inlet 120, and the second chamber portion 110 b is arranged to receive fluid from the second fluid inlet 122, while the third chamber portion 110 c is arranged to provide fluid to the first pilot valve fluid outlet 124.

As shown in FIG. 3, the valve rod 130 comprises at least a first valve rod portion 130 a, a second valve rod portion 130 b, and a third valve rod portion 130 c arranged between the first and second valve rod portions 130 a, 130 b. A diameter of each of the first and second valve rod portions 130 a, 130 b has a diameter larger than a diameter of the third valve rod portion 130 c. According to at least one example embodiment, the first and second valve rod portions 130 a, 130 b have the same diameter. According to at least one example embodiment, the first and second valve rod portions 130 a, 130 b have different diameters. The third valve rod portion 130 c may have a waist shape, or hour-glass shape, as shown in FIGS. 3-7, while the first and the second valve rod portions 130 a, 130 b may have a circular cross section with a constant diameter,

The valve rod 130 in FIGS. 3-7 further comprises a fourth valve rod portion 130 d and a fifth valve rod portion 130 e arranged between the first and the fourth valve rod portions 130 a, 130 d, A diameter of each of the first and fourth valve rod portions 130 a, 130 d has a diameter larger than a diameter of the fifth valve rod portion 130 e. The fifth valve rod portion 130 e may, similar to the third valve rod portion 130 c, have a waist shape, or hour-glass shape, while the fourth valve rod portion 130 d may have a circular cross section with a constant diameter. By having the valve rod fluid conduit inlet 132 a arranged in the fifth valve rod portion 130 e, fluid from the first fluid inlet 120 may be in fluid communication with the valve rod fluid conduit 132 within the valve rod 130.

The different positions of the valve rod 130 will now be described in further detail with reference to FIGS. 3-7. In the examples below, it is assumed that a static pressure of fluid in the first fluid inlet 120 is smaller than a static pressure of the fluid in the second fluid inlet 122.

When the combined force acting on the separating element 140 (indicated in FIG. 2a ) in a direction from the first fluid contacting area 142 at least partly towards the second fluid contacting area 143 by fluid in fluid communication with the first fluid inlet 120, and the pilot spring force of the spring, is larger than the second force acting on the separating element 140 in an at least partly opposite direction, the valve rod 130 will be in its first position as shown in FIG. 3. Here, the first fluid inlet 120, the first chamber portion 110 a and the first pilot valve fluid outlet 124 are in fluid communication with each other, while the second fluid inlet 122 is restricted from being in fluid communication with the first pilot valve fluid outlet 124 by the valve rod 130 fluidly sealing against the second sealing element 114. In other words, the second chamber portion 110 b is fluidly sealed from the third chamber portion 110 c by a sealing contact between the valve rod 130 and the second sealing element 114, According to at least one example embodiment, the third valve rod portion 130 c is arranged to be at least partly located in the first chamber portion 110 a such that the first fluid inlet 120 is in fluid communication with the first pilot valve fluid outlet 124 via the first and third chamber portions 110 a, 110 c, and the second valve rod portion 130 b is arranged to be at least partly located in both the second chamber 110 b portion and the third chamber portion 110 c such that the second fluid inlet 122 is restricted from being in fluid communication with the first pilot valve fluid outlet 124.

If the pressure difference between the static pressure of fluid in the first fluid inlet 120, and the static pressure of fluid in the second fluid inlet 122, increases, e.g. the static pressure of fluid in the second fluid inlet 122 increases and/or the static pressure of fluid in the first fluid inlet 120 decreases, the second force applied to the separating element 140 (indicated in FIG. 2a ) may overcome the combined force of the first force and the pilot spring force, and the separating element 140 will be moved further into the pilot spring chamber 163 (indicated in FIG. 2a ). Thus, the valve rod 130 will be moved from its first position to its second position, the second position of the valve rod 130 is shown in FIGS. 5-7. In the second position, the second fluid inlet 122, the second chamber portion 110 b and the first pilot valve fluid outlet 124 are in fluid communication with each other, while the first fluid inlet 120 is restricted from being in fluid communication with the first pilot valve fluid outlet 124 by the valve rod 130 fluidly sealing against the first sealing element 112. In other words, the first chamber portion 110 a is fluidly sealed from the third chamber 110 c portion by a sealing contact between the valve rod 130 and the first sealing element 112, According to at least one example embodiment the third valve rod portion 130 c is arranged to be at least partly located in the second chamber portion 110 b such that the second fluid inlet 122 is in fluid communication with the first pilot valve fluid outlet 124 via the second and third chamber portions 110 b, 110 c, and the first valve rod portion 130 a is arranged to be at least partly located in both the first chamber portion 110 a and the third chamber portion 110 c such that the first fluid inlet 120 is restricted from being in fluid communication with the first pilot valve fluid outlet 124.

In FIG. 4, an intermediate position of the valve rod 130 being in between its first and second position is illustrated. Here, neither the first fluid inlet 120, nor the second fluid inlet 122 is in fluid communication with the first pilot valve fluid outlet 124, as fluid flow from both inlets 120, 122 are restricted by the valve rod 130, and the first and the second sealing elements 112, 114. The intermediate position of the valve rod 130 may occur after the valve rod 130 has been in its first position, and hence fluid in the first pilot valve fluid outlet 124 stem from fluid from the first fluid inlet 120, although the first fluid inlet 120 is not in fluid communication with the first pilot valve fluid outlet 124. The intermediate position of the valve rod 130 may also occur after the valve rod 130 has been in its second position, and hence fluid in the first pilot valve fluid outlet 124 stem from fluid from the second fluid inlet 122, although the second fluid inlet 122 is not in fluid communication with the first pilot valve fluid outlet 124.

The second pilot valve part 201 in FIG. 2b is the same as the second pilot valve part in FIGS. 3-7, and the structure of the second pilot valve part 201 will now be described with reference to FIGS. 3-7.

As shown in FIG. 3, the second pilot valve part 201 in FIGS. 3-7 comprises a second pilot valve body 202 having a compartment 210, a low pressure fluid inlet 220 for receiving fluid from the first pilot valve part 101 via the first pilot valve fluid outlet 124, and providing fluid to the compartment 210. The second pilot body 202 further comprises a high pressure fluid inlet 222 for providing fluid to the compartment 210, and a fluid outlet 224 for receiving fluid from the compartment 210 and providing fluid to a piloted valve (as shown in FIG. 1). The compartment 210 is defined at least partly by a first end wall section 264, a second end wall section 266 arranged opposite to and facing the first end wall section 264, and a lateral wall section 268 arranged between the first and second end wall sections 264, 266.

A valve stem 230 is at least partly located inside the compartment 210. The valve stem 230 is connected to the valve rod 130 of the first pilot valve part 101 and moves together with the valve rod 130 in order to control fluid flow from the low pressure fluid inlet 220 to the fluid outlet 224 via the compartment 210, and configured to control fluid flow from the high pressure fluid inlet 222 to the fluid outlet 224 via the compartment 210.

As illustrated in FIG. 3, the second pilot valve part 201 further comprises a movable control body 250 comprised in, and movable within, the compartment 210. The movable control body 250 comprises a primary contacting area 252, a secondary contacting area 254 arranged opposite to the primary contacting area 252, and a cavity 256 for receiving fluid from the high pressure fluid inlet 222. The cavity 256 is arranged within the movable control body 250 between the primary and secondary contacting areas 252, 254. The movable control body 250 further comprises a through hole 258 extending from the primary contacting surface 252 to the secondary contacting surface 254. The through hole 258 is for receiving the valve stem 230 and the valve stem 230 is thus movable within the movable control body 250. As shown in FIG. 2b , the valve stem 230 may extend through the through hole 258.

The compartment 210 also houses a first spring 260 and a second spring 262, indicated in FIG. 3. The first spring 260 is arranged between the primary contacting area 252 of the movable control body 250 and the first end wall section 264 of the compartment 210. Hereby the first spring 260 may exert a first spring force on the movable control body 250 via the primary contacting area 252. According to at least one example embodiment, the first spring 260 is attached to the movable control body 250.

The second spring 262 is arranged between a head 232 of the valve stem 230 and the primary contacting area 252 of the movable control body 250. Hereby the second spring 262 may exert a second spring force on the movable control body 250 via the primary contacting area 252.

As illustrated in FIGS. 3-7, and indicated in FIG. 4, the valve stem 230 is connected to the valve rod 130 by a combined part 330, which extends through the second pilot valve body 202 to the first pilot valve body 102 in a combining through hole 340. The head 232 of the valve stem 230 has a cross section which is larger than the combining through hole 340 for restricting the movement of the valve stem 230 into the combining through hole 340.

In FIGS. 3-7, and as indicted in FIG. 4, the second pilot valve part 201 comprises a first sealing member 212 in the form of an o-ring 212, and a second sealing member 214 also in the form of an o-ring 214. The first sealing member 212 is arranged within the compartment 210 and a first geometrical compartment cross section 212 a of the compartment 210 tangents the first sealing member 212. The second sealing member 214 is arranged within the compartment 210 and a second geometrical compartment cross section 214 a of the compartment 210 tangents the second sealing member 214. The compartment 210 comprises a first compartment portion 210 a defined at least partly by the primary contacting area 252 of the movable control body 250, the first end wall section 264 (indicated in FIG. 3) of the compartment 210 and the low pressure fluid inlet 220, a second compartment portion 210 b defined at least partly by the second end wall section 266 and a portion of the lateral wall section 268 extending between the second end wall section 266 and a third compartment portion 210 c. The third compartment portion 210 c comprising the first and the second sealing members 212, 214 and being at least partly defined by the first geometrical compartment cross section 212 a and the second geometrical compartment cross sections 212 a, 214 a and the fluid outlet 224. The first compartment portion 210 a is arranged to receive fluid from the low pressure fluid inlet 220, and the second compartment portion 210 b is arranged to be in fluid communication with the first compartment portion 210 a via a valve stem conduit 240 within the valve stem 230 extending through the movable control body 250. The third compartment portion 210 c is arranged to be in fluid communication with the fluid outlet 224. Hereby, fluid in the first compartment portion 210 a may exert a pressure on the primary contacting area 252 for applying a force to the movable control body 250, and fluid in the third compartment portion 210 c may exert a pressure on the secondary contacting area 254 for applying a force to the movable control body 250.

The movable control body 250 is arranged inside the compartment 210, within a fourth compartment portion 210 d, such that the primary contacting area 252 faces the first compartment portion 210 a and the secondary contacting area 254 faces the third compartment portion 210 c.

The valve stem 230 in FIGS. 3-7 comprises at least a first valve stem portion 230 a, a second valve stem portion 230 b, and a third valve stem portion 230 c arranged between the first and second valve stem portions 230 a, 230 b, as indicated in FIG. 4. Each of the first and second valve stem portions 230 a, 230 b has a diameter larger than a diameter of the third valve stem portion 230 c. The third valve stem portion 230 c may have a waist shape, or hour-glass shape, as shown in FIGS. 3-7, while the first and the second valve stem portions 230 a, 230 b may have a circular cross section with a constant diameter,

The function of the pilot valve arrangement 301 and second pilot valve part 201 in combination with the first pilot valve part 101 will now be described in more detail with reference to FIGS. 3-7.

The functioning of the first pilot valve part 101 is explained above with reference to FIG. 2a , and FIGS. 3-7. Since the valve rod 130 of the first pilot valve part 101 is connected to the valve stem 230 of the second pilot valve part 201, the fluid flow inside the second pilot valve part 201 is at least partly determined by the position of the valve rod 130, and the pressure difference between the first and second fluid inlets 120, 122.

As illustrated in FIGS. 3-5, the second pilot valve part 201 is in its first state, and provides for a first fluid flow path 290, shown in FIG. 4, within the compartment and the second compartment portion 210 a, to enable the low pressure fluid inlet 220 to be in fluid communication with the fluid outlet 224. Hence, the low pressure fluid inlet 220 is in fluid communication with the fluid outlet 224 via the first compartment portion 210 a, the valve stem fluid conduit 240 within the valve stem 230, the second compartment portion 210 b, the first fluid flow path 290 and the third compartment portion 210 c.

In other word, in the first state, the first valve stem portion 230 a is arranged to fluidly seal against the inner wall defining the through hole 258 (indicated in FIG. 3) in the movable control body 250 in order for fluid in the cavity 256 in the movable control body 250 to be restricted from being in fluid communication with the third compartment portion 230 c. Furthermore, the third valve stem portion 230 c is arranged to be at least partly located in the third and second compartment portions 210 b, 210 c in order for fluid in the second compartment portion 210 b to be in fluid communication with the third compartment portion 210 c via the first fluid flow path 290. The first fluid path 290 being at least partly defined by at least a part of the lateral wall section 268 of the compartment 210 and/or the first sealing element 212 and at least a part of the third valve stem portion 230 c.

That is, in the first state, the valve stem 230 is arranged to fluidly seal against the inner wall defining the through hole 258 (indicated in FIG. 3) in the movable control body 250 by the second sealing member 214, such that the high pressure fluid inlet 220 is restricted from being in fluid communication with the fluid outlet 224.

As illustrated in FIG. 6, the valve rod 130 of the first pilot valve part 101 is in its second position and the separating element 140 is as far into the pilot spring chamber 163 as possible. Here, the valve stem 230 is as close to the first pilot valve part 101 as possible and the head 232 of the valve stem 230 is in contact with the end wall section 264. Thus, the valve stem 230 provides for a second fluid flow path 292, indicated in FIG. 6, within the compartment 210 to enable the high pressure fluid inlet 222 to be in fluid communication with the fluid outlet 224. Hence, the high pressure fluid inlet 222 is in fluid communication with the fluid outlet 224 via the cavity 256 of the movable control part 250, the second fluid flow path 292, and the third compartment portion 210 c.

In other words, in the second state, the second valve stem portion 230 b is arranged to fluidly seal against the lateral wall section 268 of the compartment 210 by the first sealing member 212 in order for fluid in the second compartment portion 210 b to be restricted from being in fluid communication with the third compartment portion 210 c. Hence, the first fluid flow path 290 is closed. Furthermore the third valve stem portion 230 c is arranged to be at least partly located in the cavity 256 and the third compartment portion 210 c in order for fluid in the cavity 256 of the movable control body 250 to be in fluid communication with the third compartment portion 210 c via the second fluid flow path 292. The second fluid path 292 being at least partly defined by at least a part of the inner wall defining the through hole 258 (indicated in FIG. 3) in the movable control body 250 and/or the second sealing member 214, and at least a part of the third valve stem portion 230 c.

That is, in the second state, the valve stem 230 is arranged to fluidly seal against the lateral wall section 268 of the compartment 210 by the first sealing member 212, such that the low pressure fluid inlet 220 is restricted from being in fluid communication with the fluid outlet 224. Hence, the fluid path 290 is closed as the second valve stem portion 230 b fluidly seals the second compartment portion 210 b from the third compartment portion by sealing against the first sealing member 212.

The movable control body 250 is allowed to be moved from a primary position, as shown in FIGS. 3-6 where the movable control body 250 still allows for a movement further towards the first end wall section 264, to a secondary position, as shown in FIG. 7 where the movable control body 250 has been moved as far as possible towards the first end wall section 264. Here, a shoulder part 250 a of the movable control body 250 rests against a recess 268 a in the later wall section 268 of the compartment 210. As illustrated in FIG. 7, the valve rod 130 and the valve stem 230 is in the same position as in FIG. 6, however the movable control body 250 has moved from its primary position, as shown in FIGS. 3-6, to its secondary position. The movement between the primary position and the secondary position is due to that a first force applied to the primary contacting area 252 (indicated in FIG. 3) by the first and second springs 260, 262 and fluid in the first compartment portion 210 a is smaller than a second force applied to the secondary contacting area 254 (indicated in FIG. 3) by fluid in the third compartment portion 210 c. This state is referred to as the second pilot valve part 201 being in its third state.

In the third state, the valve stem 230 is arranged to fluidly seal against the inner wall defining the through hole 258 in the movable control body 250 such that the high pressure fluid inlet 222 is restricted from being in fluid communication with the fluid outlet 224, and the valve stem 230 is arranged to fluidly seal against the lateral wall section 268 of the compartment 210 such that the low pressure fluid inlet 220 is restricted from being in fluid communication with the fluid outlet 224. Hence, both the first and second fluid contact paths, 290, 292 (indicated in FIGS. 4 and 6) are closed.

In other words, in the third state, the first valve stem portion 230 a is arranged to fluidly seal against the inner wall defining the through hole 258 in the movable control body 250 by the second sealing member 214 in order for fluid in the cavity 256 to be restricted from being in fluid communication with the third compartment portion 210 c. Furthermore, the second valve stem portion 230 b is arranged to fluidly seal against the lateral wall section 268 of the compartment 210 by the first sealing member 212, in order for fluid in the second compartment portion 210 b to be restricted from being in fluid communication with the third compartment portion 210 c. Hereby, none of the low pressure or high pressure fluid inlets 220, 222 are in fluid communication with the fluid outlet 224, i.e. the first and second fluid flow paths 290, 292 (indicated in FIGS. 4 and 6) are closed.

As also illustrated in FIG. 2-7, further sealing members 116 indicated in FIG. 7, are arranged within the second pilot valve body 202, e.g. for sealing fluid from the high pressure fluid inlet 222 and fluid the cavity 256 within the movable control body 250, from the first compartment portion 210 a.

The pilot valve arrangement 301 will now be described when used together with a piloted valve, similar to the manner of the pilot valve 1 and the piloted valve 3 as shown in FIG. 1. For the below examples, it is assumed that the static pressure of fluid in the first fluid inlet 120 is smaller than the static pressure of fluid in the second fluid inlet 122, and that the static pressure of fluid in the second fluid inlet 122 is smaller than the static pressure of fluid in the high pressure fluid inlet 222. Furthermore, it is assumed that the piloted valve 3 is a normally open valve, receiving fluid with a static pressure of e.g. that of the second fluid inlet 122, and delivering fluid with a static pressure of e.g. that of the first fluid inlet 120. However, the pilot valve arrangement 301 or the first pilot valve part 101 may operate a normally closed piloted valve.

As illustrated in FIG. 3, when the valve rod 130 is in its first position, and the second pilot valve part 201 is its first state, fluid from the first fluid inlet 120 will be in fluid communication with the fluid outlet 224. Hence, the piloted valve 3 (shown in FIG. 1) will receive a control feed in fluid communication with the first fluid inlet 120. Thus, the piloted valve will be fully opened and/or be moved towards a fully open position.

When the pressure difference between the first fluid inlet 120 and the second fluid inlet 122 increases, e.g. by the static pressure in the second fluid inlet 122 increases and/or the static pressure of fluid in the first fluid inlet 120 decreases, the valve rod 130 will be moved from its first position to its second position. Hereby, fluid from the second fluid inlet 122 will be in fluid communication with the first pilot valve fluid outlet 124, and the low pressure fluid inlet 220 of the second pilot valve part 201. However, the second pilot valve part 201 is still in its first state and allows for a fluid communication between the low pressure fluid inlet 220 and the fluid outlet 224, as illustrated in FIG. 5.

When the valve rod 130 is in its second position, and the second pilot valve part 201 is its first state, fluid from the second fluid inlet 122 will be in fluid communication with the fluid outlet 224. Hence, the piloted valve (shown in FIG. 1) will receive a control feed in fluid communication with the second fluid inlet 122. Thus, the piloted valve will begin to close or be closed.

When the pressure difference between the first fluid inlet 120 and the second fluid inlet 122 further increases, e.g. by the static pressure in the second fluid inlet 122 further increases and/or the static pressure of fluid in the first fluid inlet 120 further decreases, the separating element 140 will be moved as far as possible within the pilot spring chamber 163. Still, fluid from the second fluid inlet 122 will be in fluid communication with the first pilot valve fluid outlet 124, and the low pressure fluid inlet 220 of the second pilot valve part 201. However, the second pilot valve part 201 will now be moved into its second state and allow for a fluid communication between the high pressure fluid inlet 222 and the fluid outlet 224, as illustrated in FIG. 6.

When the valve rod 130 is in its second position, and the second pilot valve part 201 is its second state, fluid from the high pressure fluid inlet 222 will be in fluid communication with the fluid outlet 224. Hence, the piloted valve 3 (shown in FIG. 1) will receive a control feed in fluid communication with the high pressure fluid inlet 222. Thus, the piloted valve will either be closed in faster manner, or seal better when the piloted valve is fully closed, compared to the case when fluid from the second fluid inlet 122 is in fluid communication with the fluid outlet 224.

If the conditions for the second pilot valve part to be in its third state are fulfilled (as explained above and shown in FIG. 7), the movable control body 250 is moved to its secondary position and none of the fluid inlets 220, 222 of the second pilot valve part 201 are allowed to be in fluid communication with the fluid outlet 224.

If the static pressure of fluid in the high pressure inlet is referred to as P0, fluid from the second fluid inlet 122 in the first compartment portion 210 a is referred to as P1, the spring force of the first spring 260 is referred to Fs, and an inner and outer diameter of the first spring 260 in contact with the primary contacting area 252 are referred to as d and D, respectively, and the flow through the piloted valve (shown in FIG. 1) is denoted Q, the valve constant of the piloted valve denoted Kv, and the pressure drop due to e.g. accessories, pipes and heat exchangers in the system is denoted Dp, the following relationship applies: P0_(LIMIT) =P1+4*Fs/(pi*(D ² −d ²))+Dp P0_(MAX) =P1+Q ² /Kv ²

where P0 _(LIMIT) is the static pressure of the fluid in the fluid outlet when the second pilot valve is in its third state (i.e. no fluid communication between the high pressure fluid inlet and the fluid outlet) and P0 _(MAX) is the maximum static pressure available from the fluid distribution system, and hence the static pressure of fluid at the high pressure fluid inlet. Hence, the amplified piloted valve is prevented from oscillating due to the difference in pressure between the P0 _(LIMIT) and the P0 _(MAX).

In FIGS. 8-10, schematic illustrations of different fluid distribution systems for supplying fluid to a load are shown.

In FIG. 8, the fluid distribution system 1000 a comprises a load 1001 a, a control unit 1002 a, a supply line 1003 a for supplying fluid to the load 1001 a, an intermediate line 1005 a for transporting fluid from the load 1001 a to the control unit 1002 a, a return line 1007 a for transporting fluid from the control unit 1002 a. A static pressure of fluid in the supply 1003 a line is higher than a static pressure of fluid in the intermediate line 1005 a, and the static pressure of fluid in the intermediate line 1005 a is higher than a static pressure of fluid in the return line 1007 a.

As shown in FIG. 8, the piloted valve 1009 a or main valve 1009 a is arranged on the supply line 1003 a together with a pilot valve arrangement 1011 a as described above (indicated as 301 in e.g. FIG. 2b ) for piloting the main valve 1009 a. Furthermore, the first fluid inlet (indicated as 120 in FIGS. 2-7) to the pilot valve arrangement 1011 a is fluidly connected to the return line 1007 a, and the high pressure inlet (indicated as 222 in FIGS. 2-7) is fluidly connected to the supply line 1003 a. The second fluid inlet (indicated as 122 in FIGS. 2-7) to the pilot valve arrangement 1011 a is fluidly connected to the intermediate line 1005 a. The pilot valve arrangement 1011 a facilitates in keeping a constant pressure drop over the control unit 1002 a and in the sealing of the main valve 1009 a by allowing for the high pressure from the supply line 1003 a to be fed to the main valve.

By referring to the two equations above, in FIG. 8, Dp represents the pressure drop over the load 1001 a, Q represents the flow in the supply line 1003 a over the piloted valve 1009 a and Kv is the valve constant of the piloted valve 1009 a.

In FIG. 9, the fluid distribution system 1000 b comprises a load 1001 b, a control unit 1002 b, a supply line 1003 b for supplying fluid to the load 1001 b, an intermediate line 1005 b for transporting fluid from the load 1001 b to the control unit 1002 b, a return line 1007 b for transporting fluid from the control unit 1002 b. A static pressure of fluid in the supply 1003 b line is higher than a static pressure of fluid in the intermediate line 1005 b, and the static pressure of fluid in the intermediate line 1005 b is higher than a static pressure of fluid in the return line 1007 b.

As shown in FIG. 9, the piloted valve 1009 b or main valve 1009 b is arranged on the return line 1007 b together with a pilot valve 1011 b, here no second pilot valve part (indicated as 201 in FIGS. 2-7) is necessary and the pilot valve or the first pilot valve part (indicated as 1 in FIGS. 1 and 101 in FIGS. 2-7) is sufficient for controlling the main valve 1009 b. Here, the first fluid inlet (indicated as 120 in FIGS. 2-7) to the pilot valve 1011 b is fluidly connected to the return line 1007 b and the second fluid inlet (indicated as 122 in FIGS. 2-7) is fluidly connected to the intermediate line 1005 b. The pilot valve 1011 b facilitates in keeping the pressure drop over the control unit 1002 b constant.

In FIG. 10, the fluid distribution system 1000 c comprises a load 1001 c, a control unit 1002 c, a supply line 1003 c for supplying fluid to the load 1001 c via the control unit 1002 c, a return line 1007 c for transporting fluid away from said load 1001 c, a by-pass line 1005 c for transporting fluid between the supply line 1003 c and the return line 1007 c. A static pressure of fluid in the supply 1003 b line is higher than a static pressure of fluid in the return line 1007 b.

As shown in FIG. 10, a piloted valve 1009 c or main valve 1009 c is arranged on the by-pass line 1005 c together with a pilot valve 1011 c, here no second pilot valve part (indicated as 201 in FIGS. 2-7) is necessary and the pilot valve or the first pilot valve part (indicated as 1 in FIGS. 1 and 101 in FIGS. 2-7) is sufficient for controlling the main valve 1009 c. Here, the first fluid inlet (indicated as 120 in FIGS. 2-7) to the pilot valve 1011 c is fluidly connected to the return line 1007 c via the intermediate line 1005 c and the second fluid inlet (indicated as 122 in FIGS. 2-7) is fluidly connected to the supply line 1003 c via the intermediate line 1005 c. The pilot valve facilitates in keeping a constant pressure drop over the main valve 1009 c.

In FIGS. 8-9, the main valve 1009 a, 1009 b is normally open, and in FIG. 10, the main valve 1009 c is normally closed.

It should be noted that the control unit 1002 a-c in each of FIGS. 8-10 is a symbolic component representing any component or combination of components which provides for a controllable fluid flow, e.g. a control valve 1002 a-c, a complete branch 1002 a-c of e.g. lines, conduits, pipes and/or heat exchangers and/or another load 1002 a-c.

According to at least one example embodiment, the pilot spring may be an adjustable pilot spring. Hereby, the pilot valve and the piloted valve may be arranged in a fluid distribution system where the pressure drop over the control unit 1002 a-c varies. For example, a first pilot spring may be used in a fluid distribution system where the pressure drop over the control unit 1002 a-c is between 10 kPa and 50 kPa, a second pilot spring may be used in a fluid distribution system where the pressure drop over the control unit 1002 a-c is between 30 kPa and 150 kPa, and a third pilot spring may be used in a fluid distribution system where the pressure drop over the control unit 1002 a-c is between 80 kPa and 400 kPa.

While the pilot valve, the pilot valve arrangement, and the various fluid distribution systems are illustrated as having a particular configuration, one skilled on the art will recognize that such pilot valve, pilot valve arrangement and fluid distribution systems may include more or fewer components of different types. Indeed, one skilled in the art will recognize that the fluid distribution systems illustrated in FIGS. 8-10 have been constructed to illustrate various aspects of the present inventive concept, and therefore is presented by way of illustration and not by way of limitation. For example the present inventive concept is not limited to the specific arrangement of external and internal fluid paths fed to the first and second fluid inlets, and the high pressure fluid inlet, as shown here, but the first fluid inlet may be fed from an internal flow of the piloted valve 1009 a-c, and/or the second fluid inlet, and/or the high pressure fluid inlet may be fed from an external line somewhere else from the fluid distribution system. The external flow may e.g. derive from somewhere further upstream in the fluid distribution system. 

The invention claimed is:
 1. A pilot valve comprising: a pilot valve body comprising: a chamber, a first fluid inlet and a second fluid inlet for providing fluid to said chamber, and a fluid outlet for receiving fluid from said chamber; a valve rod arranged at least partly inside said chamber, said valve rod being configured to control fluid flow from said first fluid inlet to said fluid outlet via said chamber, and configured to control fluid flow from said second fluid inlet to said fluid outlet via said chamber; a separating element being connected to, and movable with said valve rod, said separating element having a first fluid contacting area arranged on a first side of the separating element, and a second fluid contacting area arranged on a second side of the separating element which is on an opposite side to said first fluid contacting area, said first fluid contacting area being configured to be in fluid communication with said first fluid inlet for applying a first force to said separating element, and said second fluid contacting area being configured to be in fluid communication with said second fluid inlet for applying a second force to said separating element; wherein a difference between said first and second forces controls the movement of the separating element and the valve rod in such a way that said valve rod in at least a first position provides for a fluid communication between said first fluid inlet and said fluid outlet; and in at least a second position provides for a fluid communication between said second fluid inlet and said fluid outlet, and said first fluid inlet, said second fluid inlet and said fluid outlet are each arranged on a same side of the first and second sides of said separating element.
 2. A pilot valve according to claim 1, wherein said chamber comprises a first chamber portion arranged to receive fluid from said first fluid inlet, and a second chamber portion arranged to receive fluid from said second fluid inlet, wherein when said valve rod is in said first position, said first fluid inlet, said first chamber portion and said fluid outlet are in fluid communication with each other, and said second fluid inlet is restricted from being in fluid communication with said fluid outlet by said valve rod; and wherein when said valve rod is in said second position said second fluid inlet, said second chamber portion and said fluid outlet are in fluid communication with each other, and said first fluid inlet is restricted from being in fluid communication with said fluid outlet by said valve rod.
 3. A pilot valve according to claim 2, wherein said chamber comprises a third chamber portion arranged between said first and second chamber portions, and wherein said fluid outlet is arranged to receive fluid from said chamber via said third chamber portion.
 4. A pilot valve according to claim 3, wherein said valve rod comprises a fluid conduit for guiding a fluid flow from said first chamber portion to said first fluid contacting area of the separating element in such a way that said first fluid inlet is in fluid communication with said first fluid contacting area.
 5. A pilot valve according to claim 4, wherein said fluid conduit extends through said separating element.
 6. A pilot valve according to claim 1, wherein said separating element fluidly separates said first fluid contacting area of said separating element from said second fluid contacting area.
 7. A pilot valve according to claim 1, further comprising a valve housing, wherein said valve body, said valve rod and said separating element are comprised in said valve housing, and said valve housing further comprises a pilot spring arranged to exert a force on at least a part of said first fluid contacting area.
 8. A pilot valve according to claim 7, wherein said first fluid contacting area of said separating element is facing said pilot spring, and said second fluid contacting area of said separating element is facing said chamber.
 9. A pilot valve according to claim 7, wherein said valve rod is configured to be moved from its first position to its second position if a combined force applied to said first fluid contacting area by said pilot spring and fluid in fluid communication with said first fluid inlet is smaller than said second force applied to said second fluid contacting area by fluid in fluid communication with said second fluid inlet.
 10. A pilot valve according to claim 4, further comprising at least a first sealing element and a second sealing element, and wherein said first chamber portion is arranged to be fluidly sealed from said third chamber portion by a sealing contact between said valve rod and said first sealing element when said valve rod is in said second position, and wherein said second chamber portion is arranged to be fluidly sealed from said third chamber portion by a sealing contact between said valve rod and said second sealing element when said valve rod is in said first position.
 11. A pilot valve according to claim 10, wherein said valve rod having at least a first valve rod portion, a second valve rod portion, and a third valve rod portion arranged between said first and second valve rod portions, each of said first and second valve rod portions having a diameter larger than a diameter of said third valve rod portion.
 12. A pilot valve according to claim 11, wherein when said valve rod is in its first position, said third valve rod portion is arranged to be at least partly located in said first chamber portion such that said first fluid inlet is in fluid communication with said fluid outlet via said first and third chamber portions, and said second valve rod portion is arranged to be at least partly located in both said second chamber portion and said third chamber portion such that said second fluid inlet is restricted from being in fluid communication with said fluid outlet.
 13. A pilot valve according to claim 12, wherein when said valve rod is in its second position, said third valve rod portion is arranged to be at least partly located in said second chamber portion such that said second fluid inlet is in fluid communication with said fluid outlet via said second and third chamber portions, and said first valve rod portion is arranged to be at least partly located in both said first chamber portion and said third chamber portion such that said first fluid inlet is restricted from being in fluid communication with said fluid outlet.
 14. A pilot valve according to claim 1, wherein said separating element comprises a piston or a membrane.
 15. A fluid distribution system comprising a pilot valve according to claim 1, a first fluid conduit for guiding a fluid to said first fluid inlet, a second fluid conduit for guiding a fluid to said second fluid inlet, and a third fluid conduit for guiding fluid away from said fluid outlet, wherein a static pressure of fluid in said first fluid conduit is lower compared to a static pressure of fluid in said second fluid conduit. 